In general, a hybrid electric vehicle uses both an internal combustion engine and battery power. That is, a hybrid electric vehicle efficiently combines and uses both the power of an internal combustion engine and the power of a motor.
The hybrid electric vehicle may be divided into a mild type and a hard type according to a power share ratio between the engine and the motor. In a mild type hybrid electric vehicle (hereinafter, referred to as a mild hybrid electric vehicle), a mild hybrid starter and generator (MHSG) that starts an engine instead of an alternator, or that generates electricity by an output of the engine is provided. In a hard type hybrid electric vehicle, an integrated starter and generator (ISG) that starts an engine or that generates electricity by an output of the engine, and a drive motor that drives the vehicle are separately provided.
The mild hybrid electric vehicle does not have a running mode that drives the vehicle with only a torque of the MHSG, but may assist an engine torque according to a running state using the MHSG and may charge the battery (e.g., battery of 48V) through regenerative braking. Accordingly, fuel consumption of the mild hybrid electric vehicle can be improved.
Dieseling refers to an abnormal combustion phenomenon of an engine which occurs when residual fuel within a combustion chamber spontaneously ignites as an ignition source and is referred to as run-on. In a state in which the engine is overheated, when an ignition switch is turned off, the dieseling may occur. When dieseling occurs, if the engine continues to operate, a vibration occurs and thus it is necessary to remove the vibration.
When an ignition switch is turned off, a diesel engine closes an air control valve (ACV) to block air inflow to the engine, thereby preventing dieseling. However, a driver hears the sound according to the operation of the ACV as noise, and in order to block air inflow according to operation of the ACV, a certain amount of time is required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.